The prior art is replete with devices used to cut, abrade or otherwise remove yarn wraps from cots, and underwindings from spindle assemblies. They include knife blades with sharp, externally peripheral knife edges, abrasive-surfaced elements, metal-toothed or bristled brushes and the like, which either are fixed in spaced adjacency to the rotatable element about which the wraps reside, or may be manually or mechanically moved to and held in such spaced adjacency. The need for removal of the yarn wraps may be to strip a cot of waste yarn, or to remove underwindings which otherwise would interfere with proper operation of a spindle assembly in its yarn spinning function or of adjacent assemblies. Such devices may be augmented by suction devices to remove severed yarn and fly produced in the stripping.
With the advent of new types of staple yarn, such as from diverse man-made fibers and their blends with natural fibers, the problem of the removal of yarn wraps has become more difficult to solve. Many types of such yarns have extremely high tenacities and tensile strengths, making them quite difficult to abrade and cut. These yarns have had the effect of quickly dulling knife edges and rapidly wearing abrasive, abrading implements and materials. A further effect observed is that such yarns seem to require longer and still longer intervals of time to strip them. A yet further observed effect with yarns made of thermoplastic materials is the melt fusing of their fibers due to high frictional heat developed during the stripping operation making the latter extremely difficult. In those devices employing a fixed device, such as a knife blade, constant and repeated buffetings by the yarn wraps as the element rotates not only dulls the cutting or abrading surface but wears the surface which effect quickly enlarges the distance between such surface and the element to permit larger and larger accumulations of yarn wraps to remain on the element. Further, if the device is adjustably fixed, the buffetings act to flex the device and loosen it and move it away from the rotatable element and its yarn wraps producing a similar effect to that just mentioned. When sufficiently loosened, the device is rendered inoperative, and requires positional readjustment and rigid re-fixing. All of these effects tend to mitigate against the prime advantage which one seeks in employing a fixed stripper device, that of automatically removing yarn wraps without the need for intermittant manual stripping or readjustment.
A further problem with prior art stripping devices is one of safety, and possible injury to persons adjusting or fixing the devices by an incautious coming into contact with their external peripheral knife or abrading surfaces.